Ancient Airways

According to Chatterjee, Pterodactyls lived 228 to 65 million years ago. Their sizes
ranged from a sparrow to a Cessna plane with a wingspan of 35 feet.

Texas Tech University paleontologist Sankar Chaterjee and Rick Lind, an aeronautical
engineer from the University of Florida, have developed a 30-inch robotic spy plane
modeled after a 225 million-year-old pterodactyl.

The drone, featuring a strange design of a rudder at the nose of the craft instead
of the tail, would gather data from sights, sounds and smells in urban combat zones
and transmit information back to a command center.

According to Chatterjee and Lind, this project will demonstrate a next-generation
capability of sensor emplacement using a pterodactyl as the model animal.

The unmanned, sensor-packed craft in development could soon be demonstrated using
existing materials and actuators, the researchers said. Pterodrone, the military’s
next generation of airborne drones, won’t just be small and silent – they will alter
their wing shapes using morphing techniques to squeeze through confined spaces, dive
between buildings, zoom under overpasses, land on apartment balconies or sail along
the coastline for surveillance.

Born to Fly

Pterodactyls lived 228 to 65 million years ago from the late Triassic Period to the
end of the Cretaceous Period, Chatterjee said. They dominated the Mesozoic sky, swooping
over the heads of dinosaurs. Their sizes ranged from a sparrow to a Cessna plane
with a wingspan of 35 feet. Their bodies featured lightweight bones and an intricate
system of collagen fibers that added strength and agility to their membranous wings.

“These animals take the best parts of bats and birds,” Chatterjee said. “They had
the maneuverability of a bat, but could glide like an albatross. Nothing alive today
compares to the performance and agility of these animals. They lived for 160 million
years, so they were not stupid animals. The skies were darkened by flocks of them.
They were the dominant flying animals of their time.”

Tapejara wellnhoferi, a pterodactyl from Brazil, featured a large, thin rudder-like
sail on its head that functioned as a sensory organ. Though as big as a Canada goose,
its strange design made it stand out from the Cretaceous crowd when it came to flying.
This design showed promise as a model to develop into an unmanned aerospace vehicle
called Pterodrone, which has superior agility to perform missions requiring aerial,
terrestrial and aquatic locomotion.

Divine Design

Putting the tail at the nose of an airplane would seem like a failed design. However,
Chatterjee’s research into Tapejara’s flight showed that the rudder acted similarly
to a flight computer in a modern-day aircraft and also helped with the animal’s turning
agility.

“Since the discovery of a complete Tapejara in Brazil about 10 years ago, we’ve found
they could actually sail on the wind for very long periods as they flew over the
oceans,” he said. “They spent most of their time hunting for fish. By raising their
wings like sails on a boat, they could use the slightest breeze in the same way a
catamaran moves across water. They could take off quickly and fly long distances
with little effort.”

Similarly, the drone will sail in the same manner.

Initially, Lind said he had his doubts about creating a drone built with a tail at
the nose of the aircraft.

“A vertical tail on the head is a destabilizing influence, so we immediately questioned
how Tapejara could survive in that configuration,” Lind said. “The issue of flight
control becomes quite relevant as the animal, and thus aircraft, must alter its flight
properties to take advantage of the turning capabilities presented by this vertical
tail and yet remain stable.”

Chatterjee and Lind used computer simulation models and, based off the complete skeleton
of the Tapejara, were able to unlock the secrets of flight from this strangely shaped
flying animal.

“Sankar actually contacted me about three years ago after seeing a story on the Discovery
Channel on our bird-inspired aircraft to inquire if a pterodactyl-inspired aircraft
could also be feasible,” Lind said. “We shared some discussions for a while and then
finally got serious this year once we had a common concept and could build upon that
foundation.”

Bio-inspiration has led surprisingly to a wide variety of robotic design, especially
small Unmanned Aerial Vehicles (UAVs) for urban environment that have taken cues
from birds, bats and insects. Compared with a fixed-wing aircraft, a pterodactyl
wing is a complicated structure of skin, hair, muscles, tendons, blood vessels and
nerve tissue.

A team of students from the University of Florida will begin building the aircraft
this fall. Chatterjee and Lind have submitted a joint proposal to The Defense Advanced
Research Projects Agency at the Department of Defense, which is currently under review.